1. Field of the Invention
The present invention relates to an image forming apparatus configured to form an image.
2. Description of the Related Art
An image forming apparatus is configured to form a toner image by developing an electrostatic image formed on a photoconductive drum by a developing unit, to transfer the toner image thus formed to a recording medium directly or through an intermediate transfer body, and to fix an image on the recording medium by applying heat and pressure to the recording medium to which the toner image has been transferred. A cartridge is a replacement unit in which the photoconductive drum and the developing unit are integrated and is detachably mounted to the body of the image forming apparatus.
In response to a start of the image forming apparatus, developer is agitated and rubbed within the developing unit, and a temperature of the developer gradually increases and converges to a temperature corresponding to an ambient temperature of the developing unit. It is not preferable to expose the developer to high temperature because fluidity of the developer within the developing unit is hampered for example. To that end, a conventional image forming apparatus is provided with temperature sensors at predetermined positions within the image forming apparatus. Then, if the temperature sensors detect a final threshold temperature, e.g. 100° C., the image forming apparatus is prohibited from forming an image more than what has been formed and is required to be inspected and its part is replaced and is reset by a serviceman. Or, image forming apparatuses of Japanese Patent Application Laid-open Nos. 2003-5614 and H11-272147 are provided with a cooling fan therein and an output of the cooling fan is automatically controlled such that a temperature of a developing unit is kept within a predetermined temperature range.
If a temperature sensor is disposed within a developing unit (including a case where the developing unit is built in a cartridge) to directly measure a temperature of developer, the temperature sensor ends up being replaced in replacing the developing unit. Although the temperature sensor may be used even when the developing unit is replaced in a case where the temperature sensor is disposed outside of the developing unit as disclosed in JPA Nos. 2003-5614 and H11-272147, detected temperatures of the temperature sensor largely differ depending on a state of contact and a distance between the temperature sensor and the developing unit. Even if an increase or a drop of a temperature of the developer within the developing unit may be determined from an output of the temperature sensor, it is difficult to accurately estimate an actual temperature level of the developer within the developing unit.
Then, there is proposed an arrangement in which an engage part dedicated for a temperature sensor is provided on an outer wall of the developing unit and the temperature sensor suspended from a body side by bundled wires is attached to/removed from the engage part dedicated for the temperature sensor in replacing the developing unit. In this case, however, although reproducibility of the state of contact of the developing unit and the temperature sensor is high, this arrangement requires the engage part dedicated for the temperature sensor and the dedicated bundled wires and adds another work of attaching/removing the temperature sensor in replacing the developing unit.